Generally, plastic containers are classified and subjected to disposal as noncombustible waste. In order to save labors upon waste disposal, biodegradable containers are recently under development, since such biodegradable container can be disintegrated and vanished by itself, with the aid of bacteria or the like. As such resin, polylactic acid resin (lactic acid fermentation product from starch) is readily obtainable.
With respect to polylactic acid (PLA) resin, it is known that the glass transition temperature (Tg) is as low as about 58° C. and the crystallizing speed is relatively low, so that a sufficient heat resistance of the container may not be achieved as compared to a container made of polyethylene terephthalate resin or the like. With respect to the waist portion of the container, heat resistance can be more or less improved by performing presetting during stretching (blow molding). However, practical use of a heat resistant container made of polylactic acid resin has been considered to be still problematic, due to the difficulty in terms of crystallization of non-stretched portion of the container, such as a mouth portion.
As the related art addressed to such problems, there has been proposed a container with a stereocomplex structure obtained by using a resin composition containing poly-L-lactic acid and poly-D-lactic acid in a mol ratio of 60-95:40-5 and performing stretching. Refer, for example, to Patent Document 1.    Patent Document 1: JP 2008-007736A
The conventional container described above makes it possible to increase the crystallizing speed of the non-stretched portion, with the result that the heat resistance can be improved even when poly-lactic acid resin is used. Still, however, there remains difficulty as to efficient production, in view of potential degradation of the moldability (stretching property) of such resin.